ICS1893BF Data Sheet - Release
Chapter 4 Operating Modes Overview
4.8 Auto-MDI/MDIX Crossover (New)
The ICS1893BF includes the auto-MDI/MDIX crossover feature. In a typical CAT 5 Ethernet installation the
transmit twisted pair signal pins of the RJ45 connector are crossed over in the CAT 5 wiring to the partners
receive twisted pair signal pins and receive twisted pair to the partners transmit twisted pair. This is usually
accomplished in the wiring plant. Hubs generally wire the RJ45 connector crossed to accomplish the
crossover. Two types of CAT 5 cables (straight and crossed) are available to achieve the correct
connection. The Auto-MDI/MDIX feature automatically corrects for miss-wired installations by automatically
swapping transmit and receive signal pairs at the PHY when no link results. Auto-MDI/MDIX is automatic,
but may be disabled for test purposes using the AMDIX_EN pin or by writing MDIO register 19 Bits 9:8 in
the MDIO register. The Auto-MDI/MDIX function is independent of Auto-Negotiation and preceeds
Auto-Negotiation when enabled.
ICS1893BF, Rev. E, 8/11/09
August, 2009
Copyright © 2009, IDT, Inc.
All rights reserved.
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